Computing perspective drafting machine



Jaln. 21, 1969 D. E. DEWEY ETAL 3,422,537

COMPUTING PERSPECTIVE DRAFTING MACHINE Filed May 19, 1965 Sheet I of 11 INVENTORS DONALD E. DEWEY CHARLES H. HARTMAN ROBERT D. HORN TALMAGE 0. M CARTNEY Wm M ATTORNEY Jan. 21, 1969 p. E. bEwEY ETAL 3,

COMPUTING PERSPECTIVE DRAFTING MACHINE INVENTORS DEWEY Sheet g of ll- DONALD E.

y Filed May 19, 1965 CHARLES H. HARTMAH ROBERT D. HORN TALMAGE O. MCARTNEY ATTORNEY Jan. 21, 1969 D. a. DEWEY ET.AL 3,422,537

COMPUTING PERSPECTIVE DRAFTING MACHINE I Filed May 19, 1965 Sheet 3 of 11 DONALD CHARLES H.

BY ROBERT R. HOR TALMAGE o. MCARTHEY ATTORNEY Jan. 21, 1969 D. E. DEWEY ETAL 3,422,537

COMPUTING PERSPECTIVE DRAFTING MACHINE Sheet 4 of 11 Filed May 19, 1965 EEAYITORS LES H. HARTMAN ROBERT D. HORN INV DONALD E. DEW

CHAR

TALMAGE O. MCARTNEY ATTORNEY Jan. 21, 1969 D. E. DEWEY ETAL 3,422,537

COMPUTING PERSPECTIVE DRAFTING MACHINE Filed May 19, 1965 Sheet 5 I of 11 DONALD E. DEWEY CHARLES H. HARTMAH BY ROBERT D. HORN TALMAGE 0. MCARTNEY ATTORNEY Jan. 21, 1969 0. E. DEWEY ETAL COMPUTING PERSPECTIVE DRAFTING MACHINE e of 11 Sheet Filed May 19, 1965 INVENTORS E. DEWEY CHARLES H. HARTMAN HORN ATTORNEY Jan. 21, 1969 D. E. DEWEY ETAL 3,

COMPUTING PERSPECTIVE DRAFTING MACHINE Sheet 7 of 11 Filed May 19, 1965 Jan. 21, 1969 D. E. DEWEY ETAL 3,

CO PUTING PERSPECTIVE DRAFTIN G MACHINE Filed May 19, 1965 ATTORNEY Jan. 21, 1969 D. E. DEWEY ETAL 3,422,537

COMPUTING PERSPECTIVE DRAFTING MACHINE Filed May 19, 1965 Sheet 9 of 11 Jan. 21, 1969 D. E. DEWEY ETAL CO PUTING PERSPECTIVE DRAFTING MACHINE Sheet 1 l I l l I J Sagan fi m Fllll IIIIL Filed May 19, 1965 0 A T $55288 T M M 255 m WW BEE Nx W MMM DONALD E DEWEY CHARLES H y ROBERT D.

TN. MAGE 0.

whwzoizmhom math .75 x

- XNY MQ ATTORNEY United States Patent 3,422,537 COMPUTING PERSPECTIVE DRAFTIN G MACHINE Donald E. Dewey, Charles H. Hartman, Robert D. Horn, and Talmadge O. McCartney, Seattle, Wash., assignors to Perspective Inc., Seattle, Wash., a corporation of Washington Continuation-impart of application Ser. No. 378,272, June 26, 1964. This application May 19, 1965, Ser. No. 456,995 U.S. Cl. 3318 73 Claims Int. Cl. B431 13/00 This application is a continuation-in-part of United States patent application Ser. No. 378,272, filed June 26, 1964, for Computing Perspective Drafting Machine.

The present invention relates to a drafting machine which is capable of producing various types of perspective drawings as a result of computations performed by the machine. More specifically, such a machine is capable of executing a drawing of various types in response to information for which a computer is programmed.

A modern tendency is to provide for instruction manuals, advertising purposes and manufacturing shop use drawings of perspective or axonometric type which afford better pictorial representations than orthographic views. It has heretofore been extremely difficult and time consuming to draw even an isometric view of a complicated object and it has been almost impossible to draw an accurate perspective view, especially if more than one vanishing point has been used.

It is a principal object of the present invention, therefore, to provide a machine which will execute a drawing of any desired type of perspective or axonometric view accurately and comparatively quickly with reference to the particular type of object to be drawn.

More specifically, it is an object to execute such a perspective or axonometric drawing in response to calculations performed by a computer so that it is not necessary for the operator to manipulate manually a drawing instrument to draw the perspective or axonometric view.

A further object is to provide apparatus for drawing a perspective or axonometric view of any type in response to a program for which an analogue computer has been set up so that the same type of information can be supplied to the computer, irrespective of the particular type of perspective or axonometric drawing to be produced by the apparatus.

In the production of such a perspective or axonometric view, it is an object to supply to an analogue computer information which may be obtained from two or more simple views of the object, such as orthographic views.

In general, it is an object of this invention to interpose analogue computer apparatus between means for tracing a drawing or drawings and means for executing a drawing or drawings so that the computer mechanism will effect actuation of the drawing mechanism in response to movement of the tracing mechanism. The effect of the computer on the information supplied to it to govern the drawing apparatus will depend upon the program for which the computer has been set.

An additional object is to provide auxiliary programming apparatus for the computer to provide special attributes to the drawing executed by the apparatus, such as to effect a particular rotation or tilt of a plane or to draw a particular helix for which the computer is programmed, instead of such drawing being executed in response to information supplied to the computer by a tracing operation.

An important object of the present invention is to provide apparatus which will enable complicated perspective or axonometric drawing views to be drawn by an operator having little drawing skill and knowledge of drawing tech- 3,422,537 Patented Jan. 21, 1969 niques. Moreover, it is an object to enable the computer of such apparatus to be programmed quickly and without great difiiculty.

Another object is to enable complicated perspective or axonometric views of an object to be drawn automatically in response to tracing simple orthographic views.

In providing such apparatus it is, of course, an object to include analogue computer mechanism which will effect the proper conversion of tracing movement signals into corresponding electric signals and which will integrate such electric signals in accordance with a selected program so as to actuate drawing apparatus to produce the desired type of perspective or axonometric view. In this connection it is an object to provide computer mechanism and control mechanism therefor which will enable a wide variety of perspective and axonometric views to be selected for production simply by programming the computer appropriately.

A further object of the invention is to provide apparatus on which drawings to be traced and paper on which a drawing in perspective is to be made can be mounted easily and conveniently and which will enable the drawing being produced to be observed readily at all times.

Another object is to provide in the apparatus mechanism which will enable a smooth tracing to be made manually for actuating the computer which controls the drawing mechanism.

In general, the apparatus includes a tracing board on which one or more views to be traced can be mounted in a position such that lines on such drawings can be traced manually by one or more styli, movement of which styli effect actuation of electrical input control mechanism for an analogue computer. Such computer is of a special type which can be programmed to integrate signals supplied by such input control mechanism and effect actuation of electrical output mechanism which will effect movement of drawing apparatus in a manner to produce the desired type of perspective or axonometric drawing. Programming apparatus is provided for the analogue computer mechanism to enable the desired type of perspective or axonometric view to be drawn and its size to be selected.

FIGURE 1 is a top perspective of the drawing machine of the present invention and FIGURE 2 is a similar view showing parts in phantom and illustrating rigging for effecting or controlling movement of the drawing board relative to the tracing board.

FIGURE 3 is a diagrammatic top perspective showing rigging for controlling the movement of tracing styli and their support and for producing computer input electrical signals in response to movement of the styli. FIGURE 4 is a fragmentary enlarged top perspective of one portion of the stylus support mechanism and rigging, FIGURE 5 is a top perspective of another portion of the stylus rigging, FIGURE 6 is a top perspective of a further portion of the stylus support and rigging mechanism, and FIGURE 7 is a top perspective of still another portion of the stylus rigging.

FIGURE 8 is a top perspective of the drawing mechanism of the machine shown diagrammatically and FIG- URE 9 is a top perspective of a fragmentary portion of such drawing apparatus.

FIGURE 10 is an enlarged and segmented elevation of the computer programming console of the apparatus.

FIGURE 11 is a diagrammatic representation of the relationship and integration of various components of the apparatus and the computer mechanism.

FIGURE 12A is a diagram of one portion of the computer circuit and FIGURE 12B is a wiring diagram of another portion of the computer circuit.

The computing perspective drafting machine of the present invention is composed of three principal components, namely, the input tracing component, the computer and programming component and the output drawing component. In addition to these three principal components, the machine may include accessory components, namely, a recording component for recording and storing digital tracing data, and a reproducing component by which the stored digital tracing data can be reconverted into analogue signals to be used to actuate the computer component of the machine. Also, special signals can be generated to modify the effect of the input tracing signals on the computer, or produce signals, so as to influence the output drawing component to draw special configurations.

In general, the operation of the computing perspective drafting machine involves supplying one or more views of simple type, such as orthographic projections, of an article which it is desired to portray in a perspective or axonometric view. Such a simple type of view, or views of such simple types, are mounted appropriately in the input tracing component of the machine and various elements of such views are then traced in sequence to generate corresponding input signals to the computer. Such signals are integrated and correlated and converted into appropriate output signals which are transmitted to the drawing component. Other special signals can be programmed to actuate the drawing component instead of signals generated by the input tracing component, or such special signals can be fed to the computer in addition to the signals from the input tracing component and superimposed upon such latter signals.

A preferred embodiment of the computing perspective drafting machine is shown in FIGURE 1 in which the input tracing component includes a horizontal tracing table 1 relative to which one or more styli 2 can be moved to trace a drawing or drawings mounted on the tracing board. The computer mechanism can be mounted at any convenient location, such as beneath the tracing table 1, and such computer mechanism can be programmed by the proper manipulation of controls on the console 3. Output signals from the computer will effect movement of a drawing instrument 4 relative to a drawing board on which paper to receive the drawing is mounted.

It will be noted that the tracing board 1 is disposed horizontally, or substantially horizontally, like a desk so that an operator can manipulate the styli 2 conveniently, while at the same time having the computer console 3 readily accessible. The drawing board 5 is shown as being mounted on the tracing board 1 in upright position so that the movement of the drawing instrument 4 can be observed readily by the operator. Also it is preferred that the drawing board be mounted on the tracing board or table for movement toward and away from the console 3. The drawing board is moved away from the console into the position shown in FIGURE 1 at the back of the tracing table so as to leave the tracing board unobstructed by the drawing board for manipulation of the styli 2 over it. When it is desired to move or change the paper on the drawing board, however, such board can be moved toward the console 3, before which the operator sits or stands, into a position sufficiently close to the console so that the operator can conveniently shift paper on the drawing board, remove paper from it or apply paper to it.

FIGURE 1 shows the drawing board 5 as being supported by a bridge beam 6, opposite ends of which are supported by legs 7. These legs extend downward through slots 8 in the opposite end portions of the tracing table and are supported by slides 9 in the form of collars encircling stationary support rods 10, as shown in FIGURE 2. The drawing board can be moved toward or away from the console 3 by sliding the sliders on the support rods. Movement of the drawing board through positions always parallel can be assured by interconnecting the legs 7 at opposite ends of the beam 6 by suitable rigging, such as shown in FIGURE 2.

The rigging to control the attitude of the drawing board 5 as it is shifted along the supports 10, as shown in FIG- URE 2, includes an endless line 11 extending around guide pulleys 12 adjacent to the console and guide pulleys 13 adjacent to the back corners of the tracing table, respectively. The guide pulleys 12 rotate about horizontal axes so as to provide upper and lower stretches of the line 11 at opposite ends of the tracing board. The legs 7 are connected respectively to corresponding stretches of the line 11 and the stretches extending between the pulleys .13 across the back of the board are crossed so that the two upper stretches of the line 11 at opposite ends of the tracing board move in the same direction, as indicated by the arrows, and both of the lower stretches of the line 11 move in the opposite direction, as indicated by the lower arrows. If the stretches of this line were not crossed at the rear of the tracing table, one of the legs 7 could be connected to the upper stretch of the line 11 at its end of the tracing table and the other leg 7 could be connected to the lower stretch of the line 11 at its end of the tracing table.

Connection of the drawing board mounting legs 7 by the line 11, as described above, will insure that movement of the two legs 7 will always be equal. The actual movement of the drawing board can be effected simply by pushing it in one direction or the other if the pulleys 12 and .13 are all idler pulleys, or a crank or drive motor may be provided for the axle of one of the pulleys 12 so that such pulley can be rotated to move the line 11 and, consequently, the drawing board 5.

A source drawing or drawings from which information to be fed to the computer is obtained are mounted on the tracing board 1 shown in FIGURE 1. Usually two or more of such drawings are mounted on the table in sideby-side relationship. Two styli are provided, each of which can be manipulated to trace elements of a different drawing. These styli are mounted to move along a bridge which, as shown in detail in FIGURES 4 and 5, includes upper rods 14 and 15 and a lower channel 16 connecting opposite end plates 17. As shown in FIGURE 6, the two styli 2 are carried by carriages 18 and .18, respectively. These carriages are mounted on bridge rods 14 by wheels 19 for movement along such rod. Additional wheels 20 mounted on the carriages engage a second rod 15 parallel to rod 14 to prevent tilting of the carriages relative to such rods.

The end plates 17 support the bridge for traveling transversely of its length by wheels 21 which ride on bridgesupporting tracks 22 extending in parallel relationship along opposite ends of the tracing table, respectively, as shown in FIGURE 4. Preferably such tracks are of circular cross section, and steadying or guide rollers 23 mounted on one of the bridge ends at opposite sides of the track rod engage the opposite sides of such rod to hold the bridge firmly against lengthwise movement. Any lengthwise movement of the bridge would correspond to a movement of the styli 2 relative to their respective drawings without the transmission of a corresponding signal to the computer. Consequently, it is important that any appreciable lengthwise movement of the bridge be prevented.

Since the styli 2 are carried by the bridge, any movement of the bridge along tracks 22 will correspond to a fore-and-aft movement of both styli shown relative to their respective drawings. Provision is, therefore, made to produce an electrical signal for the computer corresponding to the travel of the bridge along its tracks. In order to enable such signal to be accurate, movement of the bridge along its tracks must be controlled so that the two ends of the bridge move precisely the same distance along the two tracks 22, respectively. Both the signal generation corresponding to bridge movement and such control of movement of the opposite ends of the bridge are accomplished by the rigging shown in FIGURE 3.

The rigging line 24 is endless and includes upper and lower stretches. At three corners of the tracing table such upper and lower stretches of the line are guided by upper and lower pulleys 25 rotatable about vertical axes and the upper and lower stretches of such line are spaced apart at the fourth corner of the tracing table by a pulley 26 which rotates about a horizontal axis. At the opposite end of the line loop, the line is wound at least once around a spool 27 mounted on the shaft of a potentiometer 28.

In FIGURE 3 the upper stretches of line 24 at opposite ends of the tracing table 1 are shown as being connected to the end plates 17 of the stylus bridge. At the back of the tracing table, the upper and lower stretches of this line are crossed and thus interchanged so that the upper stretches of the line at the opposite ends of the tracing table will move in the same direction, as indicated by the arrows, and the lower stretches of these lines will move opposite to the upper stretches, as also indicated by the arrows. Such connection of the bridge end plates will, therefore, along tracks 22, its opposite ends must always move through equal distances. Alternatively, the cross of the stretches of the line 24 at the back of the tracing board could be omitted, in which case one of the traveling bridge ends would be connected to the upper stretch of the line 24 at that end of the tracing board and the other bridge end would be connected to the lower stretch of the line at the opposite end of the tracing board.

It is not necessary for one end of the line 24 to be wound around a spool 27 in order to coordinate the movement of the opposite ends of the stylus bridge along tracks 22 in the manner explained above. The purpose of winding the line 24 around the spool 27 is to effect movement of the contact element of potentiometer 28 corresponding to the travel of the bridge along the tracks. Such potentiometer movement, therefore, will correspond exactly to the movement of the two styli 2 in a fore-andaft direction relative to the drawing or drawings mounted on the tracing board 1. The electric signal thus generated in the potentiometer will be impressed on the analogue computer for utilization in effecting actuation of the drawing instrument to draw a perspective or axonometric view.

While both of the styli 2 shown in FIGURES l and 6 are carried by the traveling bridge described, the two styli can be moved independently of each other along the bridge because they are carried by independent carriages 18 and 18' shown in FIGURE 6. Provision must, therefore, be made for producing a computer input signal corresponding to each of the styli 2 independently. Such signal is produced and movement of each stylus is controlled to some extent by separate rigging for the respective styli, as illustrated in FIGURE 3 diagrammatically and in greater detail in the fragmentary views 4, 5, 6 and 7.

To a line clamp 29 on the left stylus carriage 18, as seen in FIGURE 6, is connected the upper stretch of an endless line 30 which extends about guide pulleys 31 at top and bottom of the bridge end plates 17 and within the channel 16 connecting the lower portions of the bridge end plates. This line also extends around further guide pulleys 32 at the left of FIGURE 3 which are spaced apart a short distance at the location of a stabilizing flywheel 33. To this flywheel is attached a pulley 34 located between the guide pulleys 32 around which the line 30 extends. correspondingly, endless line 30' extends around guide pulleys 31' at the top and bottom of the bridge end plates 17 and along the lower channel 16 of the bridge. In this instance the line 30' extends around spaced guide pulleys 32' and pulley 34 of flywheel 33 at the right of FIGURE 3.

The structure of the flywheel installation 33 is shown in FIGURE and the construction of the flywheel 33 is of similar character. As a stylus 2 is moved to roll its carriage 18 or 18 along the stylus bridge, the correspondinsure that, when the bridge is moved ing line 30 or 30 will turn its flywheel so that the movement of the carriage and, consequently, of the stylus will tend to be smooth because of the inertia of the flywheel driven by the line. Jerky movements which the stylus held by hand might tend to produce will thus be largely eliminated. In addition, line 30 is wrapped at least once around the spool 35 of a potentiometer 36 and line 30' is similarly wound around spool 35 of potentiometer 36. These potentiometers will thus generate signals for the computer component corresponding to the travel of the respective styli along the stylus-supporting bridge.

From the foregoing description, it will be understood that each stylus 2 shown in FIGURE 3 can be moved universally over the tracing table 1 simply by grasping the upper end of the stylus and moving it manually. Movement of either stylus parallel to the stylus bridge will simply roll the corresponding stylus carriage along the bridge. Movement of either stylus transversely of the bridge will shift such bridge transversely of its length along tracks 22. Movement of either stylus 2 in any other direction will effect a composite movement of the carriage supporting the particular stylus along the stylus bridge and the bridge along tracks 22 simultaneously. The amount of each such movement will depend upon the rectangular coordinates of the path of movement of the stylus. Such rectangular coordinates will be reflected in a corresponding movement of one of the potentiometers 36 and 36 and the potentiometer 28.

In instances where it is desired to move one of the styli 2 along a line precisely perpendicular to the stylussupporting bridge, the flywheel 33 or 33 corresponding to the stylus to be moved can be secured against rotation so as to prevent movement of the corresponding line 30 or 30. The line attached to the carriage supporting the stylus in question will hold such carriage against movement along the bridge. With the flywheel thus secured against movement, the stylus can be moved either toward or away from the operator without the necessity of the operator exerting any care to prevent movement of the stylus-supporting carriage along the stylus bridge.

A detail of brake mechanism for the flywheel 33 is shown in FIGURE 5 and a similar brake arrangement can be used for flywheel 33. A brake shoe 37' is mounted on the armature of the brake-actuated solenoid 38'. When the solenoid is energized, the plunger is reciprocated toward the flywheel to press the brake shoe 37' against its periphery for locking the flywheel. Such restraint of the flywheel will prevent line 30 from moving lengthwise of the bridge rods 14 and 15. In this instance, therefore, the right stylus 2 could be moved only perpendicular to the bridge.

While the brake-applying solenoid 38' could be energized in various ways, it is desirable to enable the brake to be applied and released instantaneously, but voluntarily, as the stylus is being moved. Consequently, a brake control trigger 39' is mounted on the right carriage 18' adjacent to its stylus and a similar brake control trigger 39 is mounted on the carriage 18 adjacent to the left stylus of FIGURE 6. In each instance the trigger is formed by the upturned end of a reciprocable rod. The trigger 39 is carried by rod 40 and the trigger 39' is carried by rod 40'. The opposite end of rod 40 carries a pulley 41 and the opposite end of rod 40' carries a pulley 41', which is hidden in FIGURE 6. At opposite sides of pulley 41 are guide pulleys 42 and at opposite sides of the pulley on carriage 18 corresponding to pulley 41 are guide pulleys 42.

A line 43 shown in FIGURES 3, 5 and 6 extends lengthwise of the bridge and between the pulley 41 on one side and the pulleys 42 on the opposite side, as shown in FIG- URE 6. In this same figure, the line 43' extending parallel to line 43 extends between the pulley 41' on one side and the pulleys 42' on the other side. As shown in FIGURE 4, one end of line 43 is anchored to the left bridge end plate 17 and the opposite end of the other line 43' is anchored to the right bridge end plate 17. The right end of line 43 is connected to a switch for controlling the energization of solenoid 38 and the left end of line 43' is connected to switch 44' which controls the energization of brake solenoid 38 shown in FIGURE 5.

In use, if the operator should desire to effect movement of one or the other stylus 2 precisely perpendicular to the bridge supporting the carriages 18 and 18', he would in grasping that stylus pull the trigger 39 or 39' corresponding to such stylus. Such pull would draw the rod 40 or 40' toward the stylus and the corresponding pulley 41 or 41' toward the opposite pulleys 42 or 42'. By such movement of the intermediate pulley, the line engaged by such pulleys would be deflected between the spaced pulleys 42 or 42' to shorten the corresponding line 43 or 43'. Such shortening of the line would actuate the brake control switch to which such line is connected for energizing the corresponding brake solenoid to press the corresponding brake shoe against its flywheel. The brake would remain thus applied as long as the trigger is pulled toward the stylus.

During the particular tracing operation, the carriage '18 or 18 corresponding to the braked line 30 or 30' would be held against movement along the bridge rods 14 and 15. Upon completion of the particular tracing movement perpendicular to the bridge, the trigger 39 or 39 would be released, whereupon the compression spring 45 or 45 would shift the corresponding pulley 41 or 41 away from the pulleys 42 or 42' to relieve the tension on the brake-actuating line 43 or 43 and enable the switch controlled by such. line to open for deenergizing the corresponding brake solenoid. It is evident, therefore, that such brake mechanism can be actuated at will quickly and conveniently.

On other occasions it may be desirable to move one or the other of the styli only parallel to the bridge rods 14 and 15. In such an event it may be desirable to secure the bridge against movement along tracks 22. For this purpose a brake such as shown in FIGURE 4 is provided which is mounted on the carriage and includes a brake shoe 46 engageable with the track 22. The shoe is shown as being mounted on an arm 47 secured on the bridge by a pivot 48 about which, the arm can swing to move the shoe toward and away from the track. Normally the arm is held in a position in which the brake shoe is retracted from engagement with the track by a tension spring 49. The brake shoe can be pressed against the track by energizing solenoid 50 to move its plunger to the left, as seen in FIGURE 4, to press against the arm 47 and swing it toward track 22 in opposition to the force of spring 49. The portion of the rod 51 to the left of the solenoid 50 is made of nonmagnetic material, while the right portion of this rod in and projecting beyond the right end of the solenoid, as seen in FIGURE 4, will be made of magnetic material, such as iron, to enable the solenoid to effect movement of it.

Energization of the bridge brake solenoid 50 can be accomplished in any of various ways. Also, additional control mechanism can be provided to modify the effect of pulling one or the other brake-operating trigger 39 or 39'. Such variation in brake control can be provided by proper setting of the brake mode control shown as the rotatable knob 52 at the right end of the console 3. The legends adjacent to this knob indicate the various types of operation of the brakes which can be selected.

When the arrow of the knob is in registry with the OH? legend, all of the brake solenoids 38, 38 and 50 will be deenergized and the solenoids 38 and 38' can be energized by pulling the triggers 39 and 39', respectively. If the arrow of the knob 52 points to the legend left on, the brake solenoid 38 will be energized to apply the brake to the flywheel 33, but this solenoid can be deenergized by pulling brake trigger 39. correspondingly, when the arrow of knob 52 is in registry with the designation right on,

Cir

the brake solenoid 38' will be energized to apply brake shoe 37' to flywheel 33, but such solenoid can be deenergized by the operator pulling on trigger 39'. When the arrow of the knob 52 points to the legend all on, all of solenoids 38, 38' and 50 will be energized to lock the bridge relative to tracks 22 and both carriages 18 and 18' relative to bridge rods 14 and '15. With the knob 52 thus set, no brakes can be released by pulling triggers 39 and 39'.

When the arrow of knob 52 points to the legend sequence the carriage brake solenoids 38 and 38 will be energized through an auxiliary circuit and the bridge brake solenoid 50 will be deenergized. Under these circumstances the bridge can be moved, but neither carriage 18 nor carriage 18' can be moved along the bridge.

Consequently, either stylus 2 can trace a vertical line on a source drawing by moving the bridge fore and aft. If trigger 39 is pulled, auxiliary circuits rendered effective by the setting of knob 52 to sequence will cause the carriage brake solenoid 38 to be deenergized and bridge brake solenoid 50* to be energized. As a result of this action, carriage 18 and the stylus 2 carried by it will be freed to be moved in a direction parallel to the bridge, but the bridge will be secured against movement along its tracks 22. Similarly, if trigger 39 is pulled, carriage brake solenoid 38' will be deenergized so that carriage 18 and the stylus carried by it can be moved along the bridge rods 14 and 15, but the bridge brake solenoid 50' will be energized so that the bridge will be locked against movement along tracks 22. With the arrow of knob 52 pointed to sequence, therefore, two brakes are in holding condition and the third brake is released. If by pulling trigger 39 or 39 one of the carriage brakes is released so that the stylus can be moved in a direction parallel to the carriage, the other carriage brake and the bridge brake 46 will be applied, so that the carriage whose trigger is pulled can be moved along the bridge, but the other carriage cannot be moved along the bridge nor can the bridge be moved along tracks 22. Such control enables one stylus or the other to be used to trace a line parallel to the bridge when its trigger is pulled, while the bridge and the carriage of the other stylus will be held stationary.

As has been mentioned previously, movement of the left stylus 2, as seen in FIGURE 3, in one direction or the other along bridge rods 14, 15 will elfect production of a tracing signal by potentiometer 36. Correspondingly, movement of the right stylus along bridge rods 14, '15 will produce a tracing signal in potentiometer 36'. Movement of the bridge along tracks 22 will produce a tracing signal in potentiometer 28. When these tracing signals are fed into the computer component of the drafting machine, they will be integrated and modified to effect energization of power drive means to move the drawing instrument 4 of FIGURE 1. As shown diagrammatically in FIGURE 8, the drive mechanism for such drawing instrument will effect movement of it universally depending upon the coordination of vertical components and horizontal components of such movement.

As shown in FIGURES 1 and 8, the drawing instrument 4 is carried by a carriage 53 which is reciprocable vertically along an upright bridge. This bridge may he formed of two parallel rods 54 connected between a top plate 55 and a bottom plate 56. The carriage may be guided on such rods by guide pulleys 57. The top and bottom plates 55 and 56 of the bridge can be mounted to travel along suitable tracks similar to the tracks 22 for the horizontal bridge shown in FIGURES 2 and 4. Drive rigging is provided for effecting movement of carriage 53 vertically along the bridge and for moving the bridge horizontally while being maintained precisely in vertical position.

The upright bridge is shifted across drawing board 5 by a line 58 which is attached to a bracket 59 on the bottom end 56 of the bridge and a bracket 60 on the top end 55 of the bridge. Such line includes a diagonal stretch extending across the drawing board substantially from corner to corner so that the parallel upper and lower stretches of the line 58 will be moved in the same direction and through the same distance. Such arrangement will insure that the two brackets '59 and 60 and, consequently, the two ends of the bridge will be moved through precisely equal distances whenever the line 58 is moved. Such line extends around guide pulleys 61 located at opposite ends of the horizontal stretches and at a further location to guide the line onto the spool 62 of a motor 63, in which is incorporated suitable reduction gearing. Such motor is controlled by the computer component of the machine.

Shifting of the vertical bridge horizontally across the drawing board will effect movement of the drawing instrument 4 to execute the horizontal components of the required drawing movement. It is necessary to shift the carriage 53 up and down along such bridge in order to execute the necessary vertical components for drawing with the drawing instrument 4. It should be possible to effect such vertical shifting of the carriage in all positions of the bridge transversely of the drawing board and any shifting of the bridge should have no tendency to shift the carriage along the bridge. Such manipulation of the carriage 53 can be effected by line 64 which has its opposite ends secured at one end of the board by anchors 65. At the opposite end of the board the line extends around guide pulleys 66 and a spool 67 driven by a reversible motor and reduction gearing 68.

Between the upper anchor 65 and the upper guide pulley 66, the line 64 passes around additional guide pulleys 69 and 70 arranged so that in engaging such guide pulleys a loop of the line can extend from the upper end portion of the bridge down to the carriage 53 in the form of a loop extending around a pulley 71 mounted on the carriage. Between the lower anchor 65 and the lower guide pulley 66, the lower stretch of line 64 also extends around guide pulleys 69 and 70 to form a second line loop extending upwardly along the vertical bridge to a lower pulley 71 on the carriage 53.

As the bridge is shifted by motor 63 in one direction or the other across the drawing board, the length of the upper stretch of line 64 and the length of the lower stretch of line 64 will remain constant as long as motor 68 is stationary because the spool 67 will serve as an anchor for the central portion of the line and the two end anchors 65 hold the opposite ends of the line against movement. Since the sum of the distances from the upper pulley 66 to the bridge and from the bridge to the upper anchor 65 will always remain constant as the bridge is moved across the drawing board, and since the distance from the guide pulleys 69 at the upper end of the bridge to the pulley 71 is always the same, the carriage 53 will not be shifted along the bridge by the upper stretch of the line 64 as the bridge is shifted. Correspondingly, the sum of the distances between the lower puley 66- and the bridge and between the bridge and the lower anchor 65 will remain the same for all shifted positions of the bridge and the distance between the lower bridge pulleys 69 and the lower bridge pulley 71 will remain constant. Consequently, again the lower stretch of the line 64 will not tend to move the carriage along the bridge as the bridge is shifted across the drawing board 5.

If the motor 68 is turned to wind the upper stretch of line 64 onto the spool 67 and to unwind the lower stretch of the line correspondingly, the loop of the upper stretch of line 64 between bridge pulleys 70 and the upper pulley 71 will shorten and the loop between the lower pulleys 70 and the lower pulley 71 will increase in length correspondingly. Consequently, the carriage 53 will be shifted upwardly along the bridge a distance equal to one-half of the extent to which the upper stretch of line 64 is shortened. Conversely, if the motor 68 is rotated in the opposite direction to shorten the lower stretch of line 64 and lengthen the upper stretch of such line, the carriage 53 will be moved downward along the bridge a distance equal to one-half of the amount that the lower stretch of line 64 is shortened. By operating motor 68 under the control of the computer mechanism, therefor, the elevational position of the drawing instrument 4 relative to the drawing board 5 can be controlled.

In drawing an object with the drawing instrument 4 by conjoint shifting of the upright bridge across the drawing board 5 and shifting of the carriage 53 along the bridge, it will be desirable in many instances for the line being drawn not to be continuous. Consequently, the drawing instrument 4 is mounted on the carriage 53 by an arm 72 which is supported by hinge 73. Such arm normally is held by a tension spring 74 in a position such that the drawing instrument 4 is spaced from the drawing board. Such arm is then swung toward the board to engage the drawing instrument 4 with the drawing surface only at such times as it is desired to mark the drawing surface.

The mechanism for depressing the arm 72 toward the drawing surface includes two pulleys 75 mounted on the carriage 53 in spaced relationship at opposite sides of the arm 72, respectively. Between the pulleys 75 is a post 76 which carries an intermediate pulley 77. The length of the post 76 is such that the pulley 77 is offset from a line joining pulleys 75. A line 78 extends along the bridge and passes beneath the two pulleys 75 and over the intermediate pulley '77. When this line is tensioned, the pulley 77 will be moved toward alignment with pulleys 75 which will effect reciprocation of post 76 to swing arm 72 toward the drawing board.

In order to be able to effect the desired shortening of line 78, the lower end of this line is anchored to an arm 79, the lower limiting position of which is established by a set screw 80. Such arm can be urged downward toward the set screw 80 by a torsion spring 81 connecting the arm 79 and an upright arm 82. The force tending to hold arm 79 down exerted through spring 81 can be altered by varying the position of arm 82 around the axis of the spring. Such swinging of arm 82 can be effected by varying the rotative position of a rotatable cam 83 engaged by the swinging end of arm 82. Such cam position can be altered by rotation of cam-adjusting knob 84. Normally the anchor arm 79 will be held by the spring 81 in the position shown in FIGURE 8, in which such arm is pressed against the end of set screw 80. When the pull on line 78 becomes sufficiently great to overcome the torsion force of spring 81, arm 79 will be lifted out of engagement with the end of the set screw.

The mechanism for tensioning line 78 includes the crank 85 swingably mounted on pivot 86 and having one arm connected to the line 78. The opposite arm has a roller 87 mounted on its end which is engageable by a bar 88 in whatever position the bridge may be relative to the drawing board 5. Such bar is mounted on two bell cranks 89 serving as parallel linkage supports for the bar. These bell cranks are also connected by a line 90' which can be reciprocated by a solenoid 91 to swing the bell cranks for depressing the bar 88 to bear on the roller 87 and swing lever 85 for pulling the upper end of line 78 up- -ward. A tension spring 92 connected to the end of line 90 opposite solenoid 91 will shift line 90 back to the left, as seen in FIGURE 8, when the solenoid has been deenergized.

When solenoid 91 is energized, it will draw line 90 to the right, as seen in FIGURE 8, a predetermined distance. Consequently, bar 88 will be depressed a predetermined distance by swinging of the bell cranks 89 and lever 85 will be swung correspondingly through a predetermined angle to pull the upper end of line 78 upward through a predetermined distance. If the anchor arm 79 connected to the lower end of line 78 is held stationary against the set screw 80 by spring 81, arm 72 will be swung toward the drawing surface as the crank 85 swings until the drawing instrument 4 touches such surface. Thereafter post 76 cannot be moved farther toward the surface and further upward pull on line 78 must swing the anchor arm 79 upward in opposition to the tension of spring 81. The amount of force exerted on line 78 to effect such swinging of the anchor arm will depend upon the force exerted by spring 81 in opposition to the pull on line '78. Changing the force of spring 81 will, therefore, change the pull on and tension in line 78 to alter the pressure exerted on pulley 77, which in turn will be proportional to the pressure exerted by the drawing instrument 4 on the drawing surface. Consequently, by regulating the force produced by spring 81 by rotating cam 84, the pressure of the drawing instrument on the drawing surface can be selected.

In many cases the drawing being produced on the drawing board will be considerably smaller than the area of the drawing board. In such instances it is desirable for the drawing instrument 4 to be raised from the drawing surface before it reaches the edge of such drawing surface. To accomplish this operation, a potentiometer 93 can be mounted on the shaft of motor 63 which effects movement of line 58 to effect translation of the bridge across the drawing board. Such potentiometer can be arranged to produce an electric signal which would deenergize the solenoid 91 when the bridge has reached a programmed limiting position of movement, either toward the left or toward the right, as seen in FIGURE 8. In addition, a potentiometer 94 can be mounted on the shaft of motor 68 so that it will operate to deenergize solenoid 91 when such motor has moved line 64 sufficiently far to raise or lower the carriage 53 along the bridge enough to move the drawing instrument 4 to the upper or lower edge of the drawing surface.

An additional potentiometer 95 is connected to the shaft of spool 62 and motor 63, the movement of which will produce a signal always corresponding to the position of line 58 and, consequently, to the position of the bridge across the drawing board. Also an additional potentiometer 96 is connected to the shaft of spool 67 and motor 68 so that it will produce a signal always corresponding to the position of carriage 53 along the bridge.

FIGURE 8 shows the various elements and rigging of the drawing component in diagrammatic fashion and FIGURE 9 shows an actual installation of the bridge driving spool 62 and motor 63 with the potentiometers 93 and 95 connected to the motor and spool shaft. This drive and sensing assembly is shown as being mounted in the lower right corner of the drawing board installation illustrated in FIGURE 1. In this instance two stretches of the line 58 are shown extending upward from the spool 62, but it will be understood that these line stretches can be guided into the pattern of FIGURE 8 simply by providing suitable guide pulleys for the line. Similarly, the spool 67 and motor 68 in conjunction with the potentiometers 94 and 96 can be mounted in the lower left corner of the drawing board structure, as shown in FIGURE 1, and guide pulleys can be provided to establish the arrangement for line 64 shown in FIGURE 8. It is not necessary that spool 67 and motor 68 be located between the upper and lower guide pulleys 66. Electrical leads for the motors 63 and 68 and for the potentiometers will be of a length sufficient to connect the drawing board to the tracing table while enabling the drawing board to be shifted fore and aft over the tracing table to be accessible to the operator, as described above.

By the use of the computing drafting machine of this invention, various types of perspective and axonometric views can be drawn and a variety of each type of view can be drawn, depending upon the capability of the computer component. It is desired to make this machine very versatile. Thus, accurate one-point, two-point or threepoint perspective views can be drawn and isometric, dimetric and trimetric axonometric projections can be drawn. In addition, source views can simply be enlarged or reduced, as could be accomplished by a pantograph. In various types of views, the drawing produced can be varied by altering the tilt of the subject, the rotation of the subject, the station point distance, the drawing rotation, or the scale, or any combination of these variables. FIGURE 11 shows a block diagram of a computer having such functions and FIGURES 12A and 12B together illustrate a representative wiring diagram for such a computer. The wiring diagram must be designed to solve equations for the horizontal and vertical components of the movement executed by the drawing instrument 4 which incorporate the various terms which it is desired to vary.

The equations which can be solved by the computer component of the present machine are cos Mil [X cos c-MY sin c) sin a [sin b(MX sin 0+MY cos c) MX; cos b] A MK2 sin b+cos b(MX sin C+MY cos 6 sin aUIIX cos cMY sin c)+ cos a [sin Mi /1X sin c-l-MY cos c) -BIX cos b] +[ZLIX sin b-l-cos b(MX sin c+MY cos 0)] where:

It will be understood that the switches, potentiometers, resistances, amplifiers and other components of the electric circuit will be selected to be of proper types and values. Various types of electrical circuits capable of solving the equations specified above could be designed.

On the console 3 shown in FIGURE 1 and in enlarged representation in FIGURE 10 are various control knobs, lights and selector switches which enable the computer to be programmed for producing the desired type of view on the drawing board 5 from source drawings on the tracing board 1.

In addition to providing simply an analogue computer for the purpose of converting and integrating input signals into drawing instrument actuating control signals, an arrangement can be provided, as shown principally in FIGURE 11, for actuating recording mechanism by movement of the styli 2 and their bridge so that the recorded data can be used at any furture time to actuate the computer of the same or a different drafting machine. The input to such a computer maybe provided in the form of digital values obtained from rotation of the spools 27, and 35 of the tracing bridge and of the tracing styli. The digital pulse generator 97 shown in FIGURE 3 is rotated with the potentiometer 28 by rotation of the spool 27 effected by reciprocation of line 24 resulting from fore-and-aft movement of the tracing bridge. Digital pulse generator 98 is rotated with potentiometer 36 by spool 35 as line 30 is reciprocated by movement of the left stylus 2. Similarly, digital pulse generator 98, is rotated with potentiometer 36 by reciprocation of the line 30' effected by movement of the right stylus 2 along the tracing bridge.

The information indicated by movement of the digital pulse generators 97, 98 and 98' is fed into the recording apparatus, as shown in block diagram form at the bottom of FIGURE 11. For each of the digital pulse generators two channels to a logic and velocity buffer 99 are provided for transmitting digital data in each direction to the logic and velocity buffer. Thus the channel CH will correspond to movement of the left styuls 2 shown in FIGURE 3 to the left, which will effect corresponding reciprocation of line 30, causing the lower stretch of this line to move to the right, as seen in FIGURES 3 and 7, for effecting counterclockwise rotation of 'the digital pulse generator 98. When the left stylus is moved to the right, thus moving the upper stretch of line 30 correspondingly and the lower stretch of line 30 to the left, the digital pulse generator 98 will be driven clockwise to produce data transmitted through the channel CH to the logic and velocity buffer.

Similarly, when the right stylus 2 is moved to the left, as seen in FIGURE 3, the corresponding portion of line 30' will be moved to the left and the lower stretch of this line will be moved to the right, which rotates digital pulse generator 98' in a clockwise direction and this data is transmitted along the channel CH to the logic and velocity buffer 99. Alternatively, if the right stylus 2 is moved to the right along the bridge, the line 30" attached to it will be moved correspondingly to the right and the lower stretch of this line will be moved to the left, as seen in FIGURES 3 and 7, so that data will be transmitted along channel CH to the logic and velocity buffer 99.

Movement of the tracing bridge away from the console 3 will shift the upper stretch of line 24 seen in FIGURE 3 rearwardly so as to rotate spool 27 in the counterclockwise direction, as seen in that figure. The data produced by rotation of the digital pulse generator 97 can be transmitted by channel CH to the logic and velocity buffer 99. Conversely, movement of the tracing bridge toward the console 3 will effect movement of the line 24 in the direction indicated by the arrows in FIGURE 3 so as to rotate spool 27 clockwise. Such rotation will effect corresponding clockwise rotation of the digital pulse generator 97 and the data thus produced can be transferred by channel CH to the logic and velocity buffer 99.

Two additional channels are provided for the logic and velocity buffer 99, one being channel CH to transmit data for recording which will effect lifting of the drawing instrument or pen 4 off the drawing surface. The other infeed channel for the logic and velocity buffer is channel CH providing a pulsing arrangement which will start or stop operation of the entire recording mechanism. The purpose of the logic and 'velocity buffer is to check the accuracy of the information received before it is recorded and also to coordinate the speed with which information is supplied through one of the channels CH to CH with the recorder 100 so that the information is not transmitted from the logic and velocity buffer to the recorder at a speed greater than the recorder is able to record such information.

The recorder is of a type which will record digital data for eight channels with respect to value and direction. Such recorder may use magnetic tape for this purpose, if desired. Such magnetic tape can be used for reproduction on the same machine used to record the data or the data could simply be recorded and subsequently used for actuating a different machine of the same type. Thus, the magnetic tape could be transported to a different location and used to actuate a computer for making a perspective drawing. In order to utilize the recorded data for such a purpose, the information is transmitted from the recorder through the appropriate channel to one of the three digital-to-analogue converters 101, and 102 and 102 shown in FIGURE 11. Converter 101 corresponds to the bridge-actuated potentiometer 28. Converters 102 and 102' correspond to the left and right stylus-actuated potentiometers 36 and 36. As shown in FIGURE 11, therefore, the X input to the computer corresponding to movement of the left stylus 2 along the tracing bridge which actuates the potentiometer 36 can be replaced by a signal supplied by the X D/A converter 102. Similarly, the X input corresponding to movement of the right stylus 2 along the tracing bridge to effect movement of the potentiometer 36' can be replaced by a signal from the X D/A converter 102'. The Y input corresponding to the movement of the tracing bridge over the tracing table to effect rotation of. potentiometer 28 at the same time would be replaced by a signal supplied by the Y D/A conveter 101. Such alternative connections from the D/A converters 101, 102 and 102 are illustrated in broken lines in the block diagram of FIGURE 11.

Whether the signals of potentiometers 28, 36 and 36 or signals from the D/A converters 10-1, 102 and 102' are used as the input for the analogue computer mechanism, it is necessary to program such computer mechanism in accordance with the equations given above in order to enable the comptuer to compute the X-abscissa and the Y-ordinate movements of the drawing instrument 4 required to produce the desired perspective or axonometric view. After the computer is programmed, it will then be necessary for the operator to trace lines on the source drawings in order to produce the drawing if the X X and Y inputs from the potentiometers are used. Otherwise the digital-to-analogue converters will actuate the computer automatically.

Programming of the computer for producing the desired type of drawing is accomplished by setting the various knobs on the console 3 of the drafting machine shown generally at FIGURE 1 and enlarged in FIGURE 10. The switches and potentiometers in the wiring diagram of FIGURES 12A and 12B are moved, at least for the most part, by the knobs numbered correspondingly on the console shown in FIGURE 10. It is usually desirable to start the programming operation at the left of the console. The power switch S1, as shown in FIGURE 10 can be moved to select any one of three positions. In the off position the entire machine will be deenergized. Rotation of the switch knob will move five switch components, each marked S1 in the wiring diagram of FIG- URES 12A and 12B.

When the knob is turned so that the arrow points to stow, the computer will actuate the drawing instrument on the plotter by movement of the carriage 53 along rods 54 and by movement of the drawing bridge so as to locate the drawing instrument 4 in one corner of the drawing board to leave the surface unobstructed for mounting of drawing paper on it. When the arrow of the switch S1 is rotated into the position shown in FIGURE 10 pointing to on, the drafting machine is in condition for operation.

The next decision which the operator must make is whether he wishes to operate the machine simply by using the potentiometer signals X input, X input and Y input to operate only the computer, or whether he wishes such signals to operate both the computer and the recorder, or Whether he wishes to operate the computer by the output from the recorder alone. Operation of the computer only by the potentiometer signals is accomplished by setting the input arrow to designate internal. When the arrow points toward internal and record, the X input, X input and Y input are connected to the computer and, also, the recorder is energized so that it will be operated by actuation of the X analogue-to-digital converter, the X analogue-to-digital converter and the Y analogue-todigital converter. When the pointer of switch S2 points to recorder playback, the broken line circuits from X D/A converter, X D/A converter, and Y D/A converter will be connected to the computer and X input, X input and Y input will be disconnected from the computer.

The next selection which the operator must make is to determine the type of view which he wishes, namely, whether perspective or axonometric, or whether he wishes to have a third orthographic view, such as a top view from source side and end views or an end view from source top and side views, for example. A fourth possibility is to operate the machine simply as a pantograph to increase or decrease the size of a source view. Such selection can be made by appropriate positioning of the function switch S3 shown in FIGURE 10 as the third knob from the left on the console 3.

It is desirable to have the drawing instrument raised from the paper at the edge of the drawing sheet on the drawing board 5. This operation of lifting the drawing instrument from the paper is accomplished electrically by programming the drawing limit using the knobs on the console 3.

The movement of the drawing instrument must be interrupted before it reaches any margin of the drawing board, as has been explained previously. Limit switch mechanism 103 for this purpose is shown in FIGURE 8 and is indicated in FIGURE 11 as a block diagram. Such limit switch mechanism in FIGURE 8 includes upper and lower limit switches adjacent to the potentiometer 94 to be actuated by line 64-, spool 67 and gearing driven by such spool. Limit switches for the right and left ends of the drawing board are shown at the right of FIGURE 8 adjacent to potentiometer 93, which can be actuated by gearing driven by spool 62 which is turned by movement of line 58.

First, the limit switch setup switch S4 is turned so that the pointer points to left, as seen in FIGURE 10. The left drawing limit switch is then adjusted while the CW and CCW lights are interchangeably illuminated to indicate that the limit has been set for the left limiting position Which the drawing instrument has been set to occupy. The pointer of switch S4 is then turned to top and the drawing instrument is located on the drawing board in the uppermost position desired. When the top drawing limit knob is turned so that the adjacent light is illuminated, the top limit will be set. Corresponding procedures are then followed to set the right limit and the bottom limit by first setting the switch S4 appropriately and, then with the drawing instrument set at the extreme location desired in each instance, the right and bottom knobs of the drawing limit control will be turned until the adjacent light is illuminated.

Next, by turning switch S5, the orientation of the source views is established. By turning switches S5 and S6, the source views and the view to be drawn on the drawing board 5 are oriented. First, the source views, which usually are two views selected from top, side and end views of the object to be drawn, are mounted on the tracing table in side-by-side relationship, one to be traced by the left stylus 2 and the other to be traced by the right stylus 2. A sheet of drawing paper of a size corresponding to the size of the drawing desired is mounted on the drawing board 5. The switch S5 is turned to indicate the type of source views being used. A dot is placed at the center of the drawing paper on the drawing board.

With the switch S5 in the appropriate position corresponding to the types of source drawings to be used, the switch S6 is turned so that its arrow points to drawing position. Next, the knobs R1 and R2 are turned until the drawing instrument is moved to the dot at the center of the drawing sheet. The drawing paper position will then be coordinated with the source views. Next, the switch S6 is turned to the designation subject position left, the appropriate knobs of R3, R6 and R9 and of R4, R7 and R10 are turned, depending upon the setting of switch S5, until the drawing instrument has been brought back into registry with the center dot of the drawing sheet. Next, with the switch S6 turned to subject position right, the appropriate one of knobs R5, R8, and R11 corresponding to the setting of knob S5 is turned, again to bring the drawing instrument back to the center dot. Switch S6 is then turned into the operate position.

There may be instances in which it is desired to superimpose some special condition on the view to be drawn. It may, for example, be desirable to portray objects on a particular plane which is inclined with reference to any subject plane. Such a special condition can be accomplished by setting the knobs S7, R12, R13, R14 and R15 of the auxiliary plane position control. As indicated by the legends on these controls, the degree of plane rotation can be selected by the knob R15. The particular direction of tilt of the plane and its location in the view to be 16 drawn can be selected by appropriate adjustment of the knobs S7, R12, R13 and R14.

In order for a perspective view of any type to be seen properly after it is drawn, it is necessary to select the proper position from which the drawing is to be viewed. A drawing which will appear accurately when viewed from a distance four feet away from the drawing plane will not appear accurate when it is viewed from fifteen or twenty feet away from the drawing plane. Consequently, the distance from the drawing plane at which the view to be drawn will appear accurately can be selected by turning knob R16, which may be turned to correspond to the distance between the expected position of the observers eye and the drawing plane.

The type of perspective view or axonometric view to be drawn will be selected by turning knob R17 to the proper subject rotation position and R18 to the proper subject tilt position. By adjustment of these knobs, the perspective can be of the one-point, two-point or three-point type if the switch S3 is aligned with the perspective designation. If the arrow of switch S3 is aligned with the axonometric designation, adjustment of knobs R17 and R18 will determine whether the view will be an isometric, a dimetric or a trimetric view.

The scale to which the drawing is to be made can be selected by turning knob R19. Thus, a large perspective view can be made from-small source views or a small perspective view can be produced from relatively large source views. In either case, the type of perspective view drawn will be accurate. The drawing rotation position to place it most advantageously on the drawing paper can be selected by turning the knob R20.

While, as has been mentioned above, the machine of the present invention is capable of producing accurate perspective or axonometric views, it may be desirable in some instances to exaggerate or diminish the drawing to be produced in one dimension. The amount of such distortion in percent of elongation or shrinkage can be selected by turning knob S10 to the appropriate proportional position. Moving switch S8 in one direction or the other will determine whether the change of scale is to be an increase or decrease. The axis about which the view is distorted, whether the left axis, the vertical axis or the right axis, can be selected by turning the knob S8 to the proper arcuate section.

In some instances it may be desirable to produce views which will give a stereoscopic effect. For such effect it is necessary to have one view observed by one eye and a different view observed by the other eye. One view can be green, the other view can be red and such views will be observed through glasses, one lens of which is green and the other lens of which is red. The green lens will obscure the green view from being observed by the eye looking through the green lens and the red lens will obscure the red view from the eye looking through the red lens. It will then be necessary to draw two different perspective views from the viewpoint of station points separated approximately two-and-a-half inches, which is the approximate space between the eyes of the observer. To draw such views of the actual size to be used, the knob S12 is set, as shown in FIGURE 10, in registry with the designation 1X. One view will then be drawn in green with the selector switch S11 deflected toward green and another view will be drawn in red with such selector switch tilted toward red.

In some instances it may be desirable to draw the perspective view on an enlarged scale to improve its accuracy and such drawing can then be reduced photographically to the proper scale for viewing. If the double size drawing is to be produced the pointer of the knob S12 should be in registry with the legend 2X to provide the proper station point locations. A triple size drawing would require the pointer to be in registry with the legend 3X, and a quadruple size drawing requires the pointer to be in registry with the legend 4X.

It is, of course, more difficult to trace a curved line on a source drawing than it is to trace a straight line. Also it is quite difiicult to generate an accurate helix. By provision of special circle/helix controls, such configurations can be drawn of any size, shape, attitude and pitch without tracing any source drawing at all. In setting up the drafting machine for drawing a circle, it is only necessary to set the knob R21 for the radius desired, the knob S13 to designate whether the circle will be drawn as if by the A left stylus or the right stylus and move the switch S14 to the left to designation circle. The circle is then actually drawn simply by turning the knob R22. Alternatively, if it is desired to draw a helix, the switch S14 is moved in the opposite direction to the word helix. The switch S15 is set to indicate whether the helix will be of left-hand or right-hand configuration and the pitch of the helix will be established by the setting of knob R23. Again, the helix is drawn simply by turning knob R22.

The various designations of S knobs correspond to the switches correspondingly labeled in FIGURES 12A and 12B. Similarly, the R knobs are provided to adjust potentiometers shown in the wiring diagram of FIGURES 12A and 12B which are numbered correspondingly. The wiring diagram shows the labeled switches, linear potentiometers and unlinear potentiometers connected in circuit with fixed resistances, fixed capacitors and amplifiers in an arrangement to accomplish the functions described above. Various parts of the wiring diagram are labeled to correlate such parts with the illustration of FIGURES 10 and 11. Such wiring diagram utilizes conventional symbols so that it is unnecessary to trace through it in this description. Also it will be understood that alternative circuits should be designed to provide a computer which would control a drawing instrument in accordance with the equations set forth above,

The technique for actually making perspective or axonometric drawings by the use of the computing drafting machine of the present invention is quite simple. A top view and a side view are mounted on the tracing table 1 in side-by-side positions convenient to be traced by the respective left and right styli 2. A piece of drawing paper of desired size is mounted on the drawing board and the machine is programmed for the desired type of view to be produced in accordance with the procedure discussed above. The left stylus and the right stylus are then moved over various portions of the source drawings to trace corresponding .lines of such drawings in sequence as far as po sible. In thus tracing the drawings, the triggers 39 and 39 adjacent to the respective styli are pulled as may be helpful in facilitating tracing of the source view parts. As the source views are being traced, the operator will also observe the drawing being produced frequently to make sure that the view being drawn is of the type desired and to make sure that mistakes are not made in tracing the source views. In referring to types of views drawn by the drafting machine of this invention, it is appropriate to use the designation perspective as a generic term covering all types of perspective and axonometric views.

It will be understood, of course, that prior to following the actual drawing technique described above the knobs on the console of the machine will be set properly to locate the switches and adjust the potentiometers for the various functions to the desired settings. In the wiring diagram FIGURES 12A and 12B all of the switches are illustrated in their positions farthest to the left to correspond to the settings of the pointers on the various knobs in FIGURE 10. Rotation of the knobs on the console of FIGURE in a clockwise direction will correspond to rotation of the similarly designated switches S and potentiometers R in the wiring diagram FIGURES 12A and 12B. It will be noted that various switches and potentiometers have more than one component and all switches in the wiring diagram bearing the same number are interconnected for conjoint rotation and the same is true of potentiometer components bearing the same designation in the R series.

It will be noted that the switch S4 is not shown in the circuit diagram of FIGURES 12A and 12B because this switch is used in connection with setting up the limit of pen movement on the drawing board. Consequently it is not a component of the computer circuit shown in these diagrams. The setup complete switch on the console simply controls lights to indicate that the desired setup has been established. The circles in FIGURE 10 above the various adjustable elements are indicator lights.

We claim as our invention:

1. A drafting machine, said machine comprising:

(a) a tracing board on which a source drawing view can be mounted;

(b) an upright drawing board above said tracing board;

(c) means mounting said drawing board for movement across said tracing board;

(d) drawing means movable over said drawing board;

(e) drive means movable to effect such movement of said drawings means;

(f) tracing means movable over said tracing and (g) computer means operable in response to movement of said tracing means over said tracing board to effect movement of said drive means for moving said drawing means over said drawing board.

2. A drafting machine according to claim 1 and comprising:

(a) said computer means converting the movement of the tracing means into perspective view coordinates; and,

(b) a control means for said computer means for imparting variable viewing distance capabilities to said perspective view coordinates in that the distance between the station point location or observation point and the perspective drawing or picture plane can be altered.

3. A drafting machine according to claim 1 andcornprising:

(a) said tracing means being capable of tracing a plurality of source views and thereby generating electrical signals;

(b) said computer means integrates the electrical signals into perspective view coordinates of the object portrayed by such source views for imparting variable viewing distance capability for altering the distance between the station point location or observation poiint and the perspective drawing or picture plane; an

(c) the computer means in integrating the electrical signals uses a control function to modify the voltage of the electrical signals with respect to each other to account for change in distance between the station point location or observation point and the perspective drawing or picture plane in a manner inversely proportional to the viewing distance and where the variable of the control function is the analogue of the viewing distance.

4. A drafting machine according to claim 1 and comprising:

(a) said tracing means operatively connected to a plurality of transducers;

(b) said transducers arranged to transmit movement of the tracing means;

(0) said computer means capable of performing mathematical operations on the output of the transducers according to the following mathematical equations and equivalent equations: (see equations); and,

(d) a control means for said computer means for imparting variable viewing distance capabilities to said mathematical operations to allow altering the distance between the station point location or observation point and the perspective drawing or picture plane:

board; 

1. A DRAFTING MACHINE, SAID MACHINE COMPRISING: (A) A TRACING BOARD ON WHICH A SOURCE DRAWING VIEW CAN BE MOUNTED (B) AN UPRIGHT DRAWING BOARD ABOVE ABOVE TRACING (C) MEANS MOUNTING SAID DRAWING BOARD FOR MOVEMENT ACROSS SAID TRACING BOARD; (D) DRAWING MEANS MOVABLE OVER SAID DRAWING BOARD; (E) DRIVE MEANS MOVABLE OVER SAID DRAWING BOARD; SAID DRAWINGS MEANS; (F) TRACING MEANS MOVABLE OVER SAID TRACING BOARD; AND (G) COMPUTER MEANS OPERABLE IN RESPONSE TO MOVEMENT OF SAID TRACING MEANS OVER SAID TRACING BOARD TO EFFECT MOVEMENT OF SAID DRIVE MEANS FOR MOVING SAID DRAWING MEANS OVER SAID DRAWING BOARD. 